Immersion: Reflexes

As you learned in anatomy, spinal reflexes are involuntary movements that occur in response to a stimulus.  Tapping a tendon with a reflex hammer stretches it. This stretch is detected by sensory afferents that relay the signal to the CNS. The signal runs peripherally through the dorsal horn of the gray matter to synapse on a motor efferent. The motor efferent returns to the same muscle, causing it to contract.

Reflexes are tested to differentiate causes of neurologic symptoms.  Problems with the central nervous system can increase reflexes while problems with peripheral nervous system or muscles decrease reflexes.

To test deep tendon reflexes, swing the reflex hammer from your wrist to strike and stretch the appropriate tendon, observing for contraction of the muscle. If you can’t elicit a reflex, try augmentation maneuvers:

    • For upper extremity reflexes: Clench the jaw and counts to 20
    • For patellar reflex: Hook the fingers of the right and left hands together and pull.
    • For Achilles reflex: Presses down lightly on your hand, as if ‘stepping on the gas
Assess each of the following reflexes, comparing side to side
Upper extremity deep tendon reflexes
Biceps With your patient’s arm flexed and the forearm supported, place your thumb over the biceps tendon. Watch for biceps contraction as you strike your thumb with the pointed end of the reflex hammer.
Triceps Your patient’s arm may be positioned with the hands on the hips OR flexed and pulled across the chest OR supported with the forearm hanging down. Strike the triceps tendon with the pointed end of the reflex hammer 2-5 cm above the medial elbow, observing for contraction of the triceps muscle.
Brachioradialis The brachioradialis muscle runs from the lateral elbow over the dorsal arm to the thumb.  Strike the radial side of the forearm above the wrist with the flat end of the hammer or place your thumb over the brachioradialis tendon and strike it with the pointed end. Watch for movement of the belly of the muscle around the elbow. You may also see a twitch of the thumb.
Lower extremity deep tendon reflexes
Patellar Place your hand on the quadriceps and strike the patellar tendon on the front of the leg below the knee.  Watch for extension of the leg or feel for contraction of the quadriceps.
Achilles With your patient seated and the feet hanging freely, support and dorsiflex one foot.  Tap on the Achilles tendon in the back of the ankle with the flat part of the reflex hammer, observing for plantar flexion of the foot.
Plantar reflex This is a ‘superficial’ rather than a deep tendon reflex. Draw a hard object lightly along the lateral foot from the heel forward and medially across the ball of the foot, observing movement of the big toe. If there is no movement, repeat with slightly firmer pressure.

Grading reflexes

Deep tendon reflexes are graded on a 0-4 scale.   Reflexes in healthy people can range from absent to exaggerated. All would be considered ‘normal’ if they are symmetric and unchanged from prior exams.

Reflexes that are asymmetric or have changed from baseline are abnormal. Reduced or absent reflexes suggest lower motor neurondisease or sensory loss. Exaggerated reflexes that are asymmetric or changed suggest upper motor neuron disease.

Grading Deep Tendon Reflexes
0 = absent
1 = present but less than average
2 = average
3 = increased
4 = clonus

Plantar reflex

The normal plantar reflex is downward movement of the toes, usually most visible in the big toe.   Slow upward movement of the toes is abnormal and indicates a problem with the brain or spinal cord.  If the patient is ticklish or uncomfortable, they may withdraw the foot – this is uninterpretable (that’s why you should start with light pressure.) The normal response can be documented as “Toes are downgoing bilaterally.”

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